Refactor Cypress tests: split into component versus full e2e tests #1032
Description
Currently we use what Cypress calls "e2e tests". Some of them actually require a working WP1 API backend (#689), even though they mock almost all other API calls and are mostly used for testing individual pages and components in the app.
We should look into converting these tests to what Cypress calls "component" tests (though I'm not sure exactly what that means...). That's different than the issue above, which seeks to just cut out the backend and mock all API calls.
Relatedly, we should create a suite of actual e2e tests, that spin up a fresh API backend and a fresh Zimfarm and test the full CUJs of creating selections and generating ZIM files.